We studied the effects of differentiation-inducers on the integrin profile and adhesive properties of K562 leukemia cells. The fibronectin (Fn) receptor integrin, α5β1, was the only integrin expressed in suspension cultured K562 cells. When the cells were exposed to 12-O-tetradecanoylphorbol-13-acetate (TPA) immunoreactivity for the β1 integrin subunit was slightly enhanced. TPA exposure also induced the appearance of the α2, α3, αv and β3 integrin subunits, but the platelet integrin subunit αIIb was not detected. On the other hand, hemin chloride-induced erythroid differentiation of K562 cells diminished the expression of the α5β1 integrin on the surface of the cells. Adhesion experiments with TPA-exposed K562 cells indicated that although the adherence to the extracellular matrix (ECM) proteins as a rule was low a few cells spread on these proteins. The present results specify the effects of differentiation inducers on the integrin profile of K562 cells and excludes the comprehension that TPA would induce expression of the platelet integrin αIIb on their surface. Our results also show, that an increased expression of a certain integrin does not necessarily lead to a comparable adhesion ability on its ligand in vitro.